The demand for water purification does not arise solely from the need for treating sewage or noxious industrial waste, nor is it necessarily directed merely toward obtaining potable water for humans and animals. Recent environment control regulations have restrained the discard of water such as that which through ordinary industrial use has appreciably increased its content of dissolved solids (which are generally inorganic or mineral compounds) as well as inhibiting discard of such liquid which has accumulated or concentrated particular toxic components.
For example, the body of water which is circulated as a coolant in many industrial or chemical plants, is then returned to a heat exchanger where part of it is evaporated in order to reduce the temperature of the remainder, which remainder is then recirculated. This evaporation step itself would increase the concentration of contained solids merely by reducing the volume of liquid. However in its travel the liquid picks up deposits or sediment from the plumbing system, and in addition, in order to minimise corrosion, foaming and scale formation (such as resulting from "hard water") various inhibitory additives are mixed into the circulating stream. These obviously contribute further to the dissolved solid content and after the latter has build up to the maximum allowable for continued circulation, it becomes necessary to discard part of the fluid mixture and replace it with fresh water (and new additives).
However this heavily loaded discard has now become an illegal pollutant when released into flowing streams or ocean. The problem is to purify it before release; and hopefully if such purification process is sufficiently successful or complete, the water may be reused indefinitely and need not be released at all.
A particular contaminant in such cooling water system is chromium which is a component of many anti-corrosive or biocide additives. Thus hexavalent chromium is a toxic substance not releasable to the environment. Other toxic components of common cooling water additives are cyanides and phosphates, which must be detoxified before release.
Purification of polluted water for purposes of reuse, whether starting with agriculture/municipal sewage or with industrial waste, has been concerned primarily with recovery of potable water, only after the initial separation and disposal of solid components in an inert state, this being considered a necessary and preliminary step for any subsequent treatment. The solids may have then been utilized to a small extent as a plant support base or land fill, but such product was not a primary purpose for effecting the separation and for the most part the undifferentiated sludge is simply separated in bulk and discarded in the manner most convenient. Purification of the aqueous phase then takes place (if at all) as a successive rather than concurrent procedure. However, it will be realized that the aqueous run-off from many and probably most water-treating procedures (even if only involving flushing) carries a quantity of solid and potentially-solid ingredients having tangible economic value if such could only be recovered in concentrated form without great expense.
Further, treatment of such masses of contaminated water in the past has been primarily on a batch basis, large bodies of water being treated with acid or other reagent in a "settling basin" or even in successive chambers and then allowed to stand for a prolonged period until spot checks shows that the supernatent was clarified. In brief, it has not been realized that by careful regulation of the parameters of a flowing stream containing charged particles, separation/purification of an impure aqueous medium could be effected in a fraction of the previous time, and also that the controls could be shifted so as to maximise the withdrawal of specific contaminants which it was desired to concentrate in the solid state. Some substances it may be desired to destroy--as microorganisms, herbicides, pesticides and inorganic toxins--or to recover, such as nitrogenous compounds, precious metals, etc. Accordingly, the control parameters of such flow-treatment can now be accommodated to a particular feed stock and with a view to how it is wished to dispose of specific contaminants.
In the past it was known to oxidise aqueous contaminants in a highly acidic medium in the presence of either mineral acid or sulfite ion (furnished by sulfur dioxide or sulfurous acid), plus a heavy metal (flocculating) ion such as furnished by iron or aluminum. Reference is made to pending application Ser. No. 403,893, filed Oct. 5, 1973 now Pat. No. 3,948,774 by the present co-invertor W. E. Lindman, which is here incorporated by reference. However, in the absence of the present knowledge of how to incorporate and utilize (especially charged) particulate matter in oxidizing the flowing contaminate stream, experience had demonstrated that (a) unlimited oxidation in the iron reaction chamber resulted in deposition of oxidation products (derived from sewage) clogging the porous iron bed and utlimately stopping the flow, (b) the trouble at this particular chamber might be relieved by excluding oxygen at this point but its necessary introduction upstream or downstream therefrom still produced inconsistent results which might vary widely from time to time and without apparent explanation. Total exclusion of oxygen from the system made the whole inoperative, but its self-distribution therein yielded peripatetic results.
However, further detail consideration at the molecular level of both interaction and lack of reaction in such systems, reinforces the observation that too often multiple potential reactants may be present in a common container and may even be swished or driven together in a liquid medium without the substrate (in this case, the solid contaminant) and the anticipated reactant (oxygen) contacting or linking together in a reactive state in appreciable quantity. As a comparison, many specialized reactions such as catalytic cracking, require a particularly tailored catalyst. By analogy, the present invention provides a particularly tailored "environment" wherein gas, liquid and solid phases are each conditioned for mutual interplay of the reacting forces.